Effects of dilute acid and steam explosion pretreatments on the cellulose structure and kinetics of cellulosic fraction hydrolysis by dilute acids in lignocellulosic materials

Fermentability of the hemicellulose-derived sugars from steam-exploded softwood (douglas fir)

“…Similar results were also reported for spruce with decreasing recoveries of mannose observed as the severity was increased from 3.44 to 3.73 (Taherzadeh et al, 1997). When Pinus pinaster was steamexploded, Carrasco et al (1994) also found better hemicellulose sugar recoveries at the lowest conditions of severity (3.55) which corresponded to a temperature of 190°C. However, both of these studies (Carrasco et al, 1994;Taherzadeh et al, 1997) used H 2 SO 4 as a catalyst.…”

“…When Pinus pinaster was steamexploded, Carrasco et al (1994) also found better hemicellulose sugar recoveries at the lowest conditions of severity (3.55) which corresponded to a temperature of 190°C. However, both of these studies (Carrasco et al, 1994;Taherzadeh et al, 1997) used H 2 SO 4 as a catalyst. As the pretreatment severity increased from low to high (Table II), the percentage of total hemicellulose sugar recovery detected in the water soluble fraction dropped to 66% and 43%, respectively, for the medium-and the highseverity pretreated samples.…”

“…Pretreatment techniques such as steam explosion were generally optimized to produce an insoluble fraction rich in cellulose that was easily hydrolyzed using cellulases. Most wood residues were treated at temperatures ranging from 200 to 220°C at cooking times of 3 to 5 min and 2 to 3% of SO 2 (Carrasco et al, 1994;Clark and Mackie, 1987). These conditions usually led to at least partial degradation of the hemicellulose-derived sugars and significant solubilization and transformation of lignin-related chemicals (Ando et al, 1986).…”

Development and Characterization of an Environmentally Friendly Process Sequence (Autohydrolysis and Organosolv) for Wheat Straw Delignification

“…Removal of amorphous materials (lignin, hemicellulose) from lignocellulosic fractions and rearrangement of the remaining components have been associated with improved crystallinity [51]. According to the other works, increases of the crystallinity index values were observed following steam explosion and microwave digestion of sorghum bagasse [52,53]. For the crystallinity index obtained after the organosolv process was 53.59%, indicating damages on the fiber structure and a more exposed cellulosic surface.…”

Hydrothermal pretreatment of lignocellulosic biomass

“…As lignin is reorganized and hemicellulose solubilized, the molecular tensions holding crystalline cellulose together are weakened. This allows formerly amorphous cellulose to be incorporated into the crystalline structure, leading to an increase in the overall crystallinity (Shevchenko et al, 2001;Carrasco et al, 1994;Josefsson et al, 2001). However, this change may be dependent on process parameters, as other researchers have found that there is no change in crystallinity (Dekker and Wallis, 1983).…”